Surface Energy of Food Contact Materials and Its Relation to Wheat Dough Adhesion

Abstract

This study investigates the influence of the surface free energy (SFE) on the adhesion behaviour between wheat dough and bakery-relevant food processing surfaces. In doing so, the contact time and production-related changes of the adhesive and the adherend were taken into account. The adhesion measurements were conducted by means of previously developed methods (modified Chen/Hoseney, contact time measuring cell), whereby the force required for separating the dough from the surface after processing-relevant contact times was determined applying a texture analyzer. The SFE was determined by contact angle measurements. The SFE values for the examined materials are ranged between 5.5 ± 0.81 and 42.7 ± 0.88 mN/m. A strong linear correlation between the SFE of the bakery surfaces and their adhesion to dough could be determined after a certain contact time (≥ 1 min) (r = + 0.96 for surfaces with Sa > 20 μm; r = + 0.94 for surfaces with Sa < 20 μm). Bakery surfaces with energy values σsolid surface, total > 30 mN/m including a polar content indicated a strong interaction with wheat dough, which was confirmed by high adhesion values. Production-related changes to the processing surfaces showed a great impact on the adhesion behaviour: e.g. the abrasion of proofing cloths caused a higher amount of protruding fibres, which operate as a separating layer, resulting in a decrease of dough adhesion even after long contact times. The results in this study emphasize the importance of the SFE in the development of processing surfaces for the baking industry.

Understanding stickiness in sugar‐rich food systems: A review of mechanisms, analyses, and solutions of adhesion

“…For example, -NH 2 -is more of an electron acceptor that can form a strong bond with an electron donor (e.g., -COOH) from another surface (Bialopiotrowicz & Jańczuk, 2002). Hydrogen bonding may be considered a special type of Lewis acid-base interaction, which can happen between a polar food material (e.g., caramel and wheat dough) (Laukemper et al, 2021;Wang & Hartel, 2021a) and a polar surface rich in -OH, -NH, -HF, or -C = O groups (e.g., wood or paper).…”

“…The equipment involved in food processing is almost entirely made of stainless steel (Avila-Sierra et al, 2019). Conveyor belts for confections are usually made of flexible materials such as thermoplastic polyurethane, polyolefins, polyesters, and silicone (Laukemper et al, 2021). Food packaging and serving materials cover a wide range of papers, ceramics, acrylics, plastics, and sometimes metals.…”

“…With high-energy surfaces such as paper and glass, cohesive failure readily happened, meaning that the adhesive forces outweighed the cohesive forces within the bulk of the caramel or chocolate (Keijbets et al, 2009;Wang & Hartel, 2021a). In general, when selecting materials for conveyor belts and packaging, a low surface energy (<25-30 mJ/m 2 ) is preferred (Laukemper et al, 2021). Materials made of fluorine and silicon compounds, such as Teflon and silicone, are typical examples of antisticking materials.…”

Bioactive Electrospun Fibers of Poly(ε-Caprolactone) Incorporating α-Tocopherol for Food Packaging Applications

“…Materials for food contact applications require specific wettability, which is regulated by surface free energy and surface structure [ 50 ]. It is well known that a low surface energy induce a hydrophobic character, with low wettability reflected in high contact angles.…”

“…Strong increase of tocopherol content from 5 to 20 wt% had only marginal effect on increasing the contact angle from 138.9 to 142.1°, and this could be due to increased roughness of the fibers, as shown by AFM micrographs in Figure 6 and the corresponding histograms in Figure 7. Materials for food contact applications require specific wettability, which is regulated by surface free energy and surface structure [50]. It is well known that a low surface energy induce a hydrophobic character, with low wettability reflected in high contact angles.…”